This car starts from cold fine and then after about 1 or 2 minutes of running it will run very roughly as though over rich. It does this for about 30 secs and then settles back to pretty normal for the day once hot!

Its been to both dealers here in Perth Western Australia who have given up basically. I found the injector O rings were mangled and the plug gaps were double the specs. Correcting both has improved the idle but the problem persisted.

I have a Pico scope and found that indeed when the engine is running roughly the pulse width goes off the screen and by the time I'd fiddled with the time base to get it on screen the pulse width was coming back to normal and the engine starting to run ok again. Even when fully warm the width is about 4.25mSec which is very slightly higher than any other car I've checked as they are invariably 3.5mSec.

I haven't monitored it from a cold start as yet and looking at the oxygen sensors waveforms was inconclusive to me at least! As I've found oxygen sensors can do strange things I tried some new ones however the problem remains though the idle once it settles again is smoother.

Maybe the MAP is momentarlily giving a false reading with the first glimmer of heat in the engine?

Any ideas or am I missing something? It seems to me that something is telling the ECU to grossly increase the pulse width for that period or maybe an ECU problem. If so it would be the first one I've ever had in 12 years, hence I'm sceptical.

The dealer advised the owner that the problem was a mechanical one requiring the cylinder head to be removed. I'm not convinced to say the least as I cannot think how anything mechanical could be so transient.

Hope someone can assist!

Mark Dyson